The present invention relates to a disposition structure of an exhaust-gas purification device to purify exhaust gas from an internal combustion engine of a vehicle by using deoxidizer.
It is generally known that the nitrogen oxide (NOx) contained in the exhaust gas from the internal combustion engine (diesel engine, gasoline engine, etc.) of vehicles, such as an automotive vehicle, is purified by a NOx deoxidizing catalyst which is disposed in an engine exhaust pipe.
It has been recently proposed that the ammonia is used as the deoxidizer for improving the purification efficiency by the NOx deoxidizing catalyst. For example, if the urea water solution, as the deoxidizer, is added into the exhaust pipe upstream of the deoxidizing catalyst, the added urea water solution is heated and resolved by the exhaust gas of the engine, resulting in producing ammonia. This ammonia acts as the deoxidizer so that the purification of NOx in the exhaust gas can be promoted. Herein, instead of resolving the urea, the ammonia may be directly added into the exhaust gas upstream of the deoxidizing catalyst.
In a case where the above-described exhaust-gas purification system is applied, it may be necessary to provide a tank (deoxidizer tank) to accommodate the urea water solution or the ammonia, which is supported at a vehicle body. Japanese Patent Laid-Open Publication No. 2006-242092, for example, has proposed such a disposition structure (layout) of the deoxidizer tank.
According to the layout disclosed in the above-described patent publication, a space inside an engine room or a side cowl, below a font seat in a vehicle compartment, inside a bumper at a vehicle end, or a vehicle-body frame can be properly utilized. Thus, the volume of the deoxidizer tank can be increased, including providing plural tanks, and thereby the frequency in supply of the deoxidizer can be properly reduced.
Meanwhile, as well known, the ammonia has some toxicity and strong irritant odor. Accordingly, in case of a breakage of the deoxidizer tank, the leaking deoxidizer has to be prevented surely from entering into the vehicle compartment. It is also known that while the temperature at which the urea is resolved into the ammonia easily (the urea resolution temperature) is about 150 degrees C., the small amount of resolved ammonia gas may be produced even at the normal temperature. Therefore, it is preferable that not only the ammonia but the urea water solution be prevented surely from entering into the vehicle compartment.
In the conventional layout, however, the deoxidizer tank is disposed above the vehicle-body floor, so that there is a concern that the deoxidizer leaking from the broken tank would enter into the vehicle compartment. Particularly, in the engine room are provided several components and members with the surface temperature which is higher than the urea resolution temperature. Accordingly, in a case where the deoxidizer tank is disposed in the engine room, the leaking urea water solution tends to be resolved easily so as to produce the ammonia, resulting in a bad situation.
Further, there is another concern that in case of supplying the deoxidizer into the deoxidizer tank, the fuel into a fuel supply port which opens to the outside of the vehicle compartment, a wiper washer liquid into a pouring port which opens to the inside of the engine room, or the like, the wrong liquid would be supplied into the wrong port by mistake, for example, the fuel or the washer liquid are poured into the supply port of the deoxidization tank with confusion of the ports. Thus, it may be required that this mistake be surely prevented when laying out the deoxidizer tank.